Composite materials having enhanced mechanical and physical properties over conventional polymers are well known. For example, polyester reinforced with fiberglass has been used where enhanced physical properties are necessary in load bearing structures. However, such fiber reinforced plastics have certain drawbacks. Generally, a minimum of thirty percent by weight of reinforcing fiber is required for enhanced mechanical properties. Since the length of the fibers necessary to impart structural improvement is greater than one centimeter, the processability of fiber reinforced plastics is limited.
The limits of fiber reinforced plastics have led to efforts to produce a reinforced plastic by forming a composite with a reinforcing material present on the molecular level. Attempts were made to achieve the molecular composite by physically melt mixing thermoplastic nylon 66 and a finely pulverized reinforcement, poly-p-phenylene terephthalamide. M. Takayanagi, T. Ogata, M. Morikawa and T. Kai, J. Macromol. Sci. Physics 817, 591 (1980). The physical mixing process was limited by the inability to achieve dispersion on the molecular level. Others attempted to codissolve the reinforcing material poly-p-phenylene-benzobisthiazole with a plastic material. W. F. Hwang, D. R. Wiff, C. L. Benner, and T. E. Helminiak, J. Macromol. Sci-Physics 822(2), 231 (1983). U.S. Pat. No. 4,377,546 to Helminiak et al. discloses a composite material cast from methane sulfonic acid. Similarly, U.S. Pat. No. 4,631,318 discloses a composite material of poly-p-phenylene benzobisthiazole and nylon processed from a solution of methane sulfonic acid. The method of codissolving the rigid polymer and the matrix polymer is limited because the only suitable solvents are very strong acids.
U.S. Pat. No. 4,614,784 discloses a semi in situ composite material wherein a rigid rod-like liquid crystalline polymer is dissolved in a polymerizable solvent which is subsequently polymerized producing a polymeric liquid crystalline or isotropic alloy. However, one drawback to the semi in situ process is the limited solubility of suitable rigid rod polymers in polymerizable solvents. This drawback is overcome in the present invention by a complete in situ process, wherein precursors to the rigid rod polymer are dissolved in precursors to the matrix polymer and the polymerizations are carried out in sequence or simultaneously. Additionally, the in situ composite process of the present invention results in unexpected improvement in mechanical and physical properties of the in situ composite material with lower amount of the rigid rod polymer present in the composite material.
Accordingly, one object of the invention is to provide an in situ composite material with enhanced mechanical and physical properties.
Another object of the invention is to provide a method for making such an in situ composite material.
A further object of the invention is to provide a method of producing manufactured articles made out of the in situ composite material.
A still further object of the invention is to provide a process for producing manufactured articles made from the composite material adaptable to standard production techniques, such as the use of a polymer processing extruder.